The overall goal of this research is to understand the physiological processes governing gonadotropin releasing-hormone (GnRH) secretion in primates. The specific aims of the proposal are to identify the cellular and molecular mechanisms mediating estradiol's (E2) action on GnRH neurons and to examine the role of galanin in GnRH/luteinizing hormone (LH) release. Experiments will be done in female monkeys, Macaca nemestrina. To understand more about how GnRH neurons control LH release, I will use single-label in situ hybridization to determine if E2 regulates GnRH gene expression and double-label in situ hybridization to determine if GnRH neurons coexpress GnRH receptor. I will also determine if E2 regulates GnRH receptor expression in the hypothalamus and/or pituitary. To elucidate the role of galanin in GnRH/LH secretion, I will attempt to confirm galanin stimulates LH secretion. I will do this by determining if a peripheral injection of galanin increases LH release in monkeys maintained on follicular phase levels of E2 and if peripheral infusion of galantide, a galanin antagonist, blocks LH secretion in monkeys at the time of an E-induced LH surge. I will attempt to confirm that GnRH neurons do not coexpress galanin, but that galanin mRNA levels are regulated by E2 in other hypothalamic neurons. If this finding is confirmed, I will determine if E2 acts directly on galanin neurons by seeking coexpression of estrogen receptors in GnRH neurons. Finally, to determine if galanin acts directly on GnRH neurons, I will seek coexpression of galanin (R1) receptor in GnRH neurons and determine if it is regulated by E2.